Wireless communication has increased explosively in the number of subscribers centering around a voice service during the last ten years. An example of such a communication system includes a GSM (Global System for Mobile Communications). On the other hand, in recent years, the needs for high speed data communication as well as the voice service have been increasing. Also in the GSM, a method that uses conventional GMSK (Gaussian Minimum Shift Keying) modulation which is constant envelope modulation is being scheduled to shift to an EDGE (Enhanced Data for Global Evolution) method that uses 8-level PSK (Phase Shift Keying) modulation which is multi-level modulation and non-constant envelope modulation. An apparatus that copes with this EDGE method must be a dual mode apparatus that copes with two methods of a conventional GSM method (constant envelope GMSK modulation) and an EDGE method (non-constant envelope 8-level PSK modulation).
An example of a transmitter that can cope with two modulation formats of these constant envelope modulation and non-constant envelope modulation is disclosed in a Patent document 1.
[Patent Document 1] JP-A No. 193430/1995